1. Field of the Invention
The present invention relates to a jacketed, multi-member cable. More particularly, the present invention relates to a multi-member cable with a strand lay of the cable elements that switches directions along the length of the cable, wherein the cable has features for improved mid-span access and cost savings in manufacturing.
2. Description of the Related Art
A multi-member cable 9, having many buffer tubes 17 and/or power conductors 21 bundled together, is known in the existing arts. FIG. 1 is a perspective view of a typical multi-member cable 9 having a six-around-one configuration, wherein six buffer tubes 17 and/or power conductors 21 are located around a central strength member 25. In FIG. 1, reference numeral 11 denotes an outer jacket. The outer jacket 11 surrounds an armor layer 13. The armor layer 13 surrounds a cable core 15.
In practice, the cable core 15 is made up of separate cabling elements, such as one or more buffer tubes 17 with loose fibers 19 and/or one or more insulated power conductors 21 with central conductors 23. FIG. 1 shows a six-around-one configuration, or more precisely six cable elements around the central strength member 25. The strength member 25 may be formed as a glass-reinforced plastic (GRP) rod or a fiber-reinforced plastic (FRP) rod. First and second binding tapes 35 and 37 wrap around the cable core 15. Commonly, the first and second binding tapes 35 and 37 are made of flat, polyester tape.
During the manufacturing process of the multi-member cable 9, the stranding of the cable core 15 changes directions, from clockwise to counterclockwise in a repeating pattern. The direction change point in the stranding is often called a switchback, or strand lay reversal point. Because the cable core 15 has switchbacks, the first and second binding tapes 35 and 37 are needed to hold the cable core 15 together during the manufacturing process, e.g., before the armor layer 13 is applied, and/or before the outer jacket 11 is extruded onto the cable core 15.
FIG. 2 is a perspective view of a long length of the multi-member cable 9 with the outer jacket 11 removed to show the inner stranding. A first switchback 27 shows a transition of the strand lay to a clockwise direction (as viewed from the left side of the FIG. 2 to the right side of FIG. 2). A second switchback 29 shows a transition of the strand lay to a counterclockwise direction. A distance A exists between the first switchback 27 and the second switchback 29. The distance A is typically related to the diameter of the multi-member cable 9, e.g., the number of cable elements which make up the cable core 15, and/or the size of the cable elements. Typical diameter ranges are 300 mm to 1,500 mm, such as 400 mm to 1,300 mm.
A third switchback 31 shows a transition of the strand lay from the counterclockwise direction back to the clockwise direction. A distance B exists between the second switchback 29 and the third switchback 31. The distance B is equally to the distance A. The pattern of strand lay reversals continues along the length of the multi-member cable 9. For example, a fourth switchback 33 transitions the strand lay from clockwise to counterclockwise, and so on.
During the manufacturing process of the multi-member cable 9, the stranding of the cable core 15 needs to held together prior to the jacketing process. If the cable core 15 is not held together, the cable elements will separate at the switchbacks 27, 29, 31, 33, etc. One or more binding cords or tapes, such as the first and second binding tapes 35 and 37, are wrapped around the cable core 15, as the cable core 15 is stranded to keep the cable core 15 intact. The intact cable core 15 is fed into a machine to apply the armor layer 13 and/or into a machine to extrude the outer jacket 11 over the cable core 15.
Additional background art can be seen in U.S. Pat. Nos. 5,268,971; 5,905,834; 7,049,523; 7,259,332; 8,855,454 and 8,909,014 and in U.S. Published Application No. 2008/0271919, each of which is herein incorporated by reference.